1. Field of the Invention
This invention relates to a method and apparatus in practical use, thereof, for detecting the traveling position and/or direction of an unmanned vehicle traveling by means of an autonomous guidance system.
2. Description of the Prior Art
An unmanned vehicle automatically travelling on a plant floor without using a railed track has recently been developed and put into practical use. The well-known method for controlling the travel of the unmanned vehicle, utilizes as the guiding information an electromagnetic wave generated by a current flowing in a wire provided under the floor. Such controlling method, however, needs great expense for the wire burying work and is difficult to carry out maintenance and inspection and moreover not easy to change the course on which the vehicle travels. There is an autonomous guidance method as a countermeasure for the above defects, which mounts on the vehicle an arithmetic unit which accumulates and computes pulses corresponding to the number of rotations of right and left wheels, the vehicle being set at a start point on the course on which the vehicle is to travel, sequentially counting the pulse number simultaneously with a start of the vehicle, detecting the position and direction of the vehicle, and guiding the vehicle to travel accurately along the predetermined course, thereby correcting at the fixed points on the way of the course the position and direction of the vehicle to eliminate the cumulative errors.
The method for controlling the travel of unmanned vehicle by use of the aforesaid autonomous guidance method is that intensities of magnetic fields of magnets disposed at the fixed points on the travel course for the vehicle are detected by a plurality of magnetism detection elements being disposed in the transverse direction of the vehicle, and the travelling position and/or direction of the same when passing the fixed points are computed separately on the basis of an output of each magnetism detection element, thereby correcting the detected traveling position and/or direction in accordance with the computed values (the Japanese Patent Laid-Open No. 58-11030).
The above conventional method, however, disposes each magnet at each fixed point spaced at a predetermined interval along the traveling course, whereby the traveling position and/or direction cannot be detected until the vehicle having passed on the two magnets. Hence, a time delay occurs, thereby creating the problem in that the non-linear travel of the vehicle within the time-delay causes an error.